To understand control of gene expression in higher organisms, we are studying the structure and regulation of collagen genes, initially in chicken but ultimately in humans. Complementary DNA to type I and type II procollagen mRNAs will be used to identify amplified DNA restriction fragments containing collagen sequences as well as sequences surrounding the structural gene. Restriction fragments will be enriched for collagen genes prior to amplification by preparative gel electrophoresis. The transcription pattern will be analyzed to identify promoter regions in different tissues and at different stages of development to define the size of the primary transcription product. The structure of chromatin containing specific genes which are being expressed will be studied, first with globin and later with collagen. A comparison will be made between nuclear RNA in vivo and that obtained in isolated nuclei and in chromatin using purified chick RNA polymerase II as a probe.